Pollination and parasitism in functionally dioecious figs

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Abstract

Fig wasps (Agaonidae: Hymenoptera) are seed predators and their interactions with Ficus species
(Moraceae) range from mutualism to parasitism. Recently, considerable attention has been paid to
conflicts of interest between the mutualists and how they are resolved in monoecious fig species. However,
despite the fact that different conflicts can arise, little is known about the factors that influence the
persistence of the mutualism in functionally dioecious Ficus.We studied the fig pollinator mutualism in 14
functionally dioecious fig species and one monoecious species from tropical lowland rainforests near
Madang, Papua New Guinea. Observations and experiments suggest that (i) pollinating wasps are
monophagous and attracted to a particular host species; (ii) pollinating and non-pollinating wasps are
equally attracted to gall (male) figs and seed (female) figs in functionally dioecious species; (iii) di¡ering
style lengths between gall figs and seed figs may explain why pollinators do not develop in the latter ;
(iv) negative density dependence may stabilize the interaction between pollinating wasps and their
parasitoids; and (v) seed figs may reduce the search efficiency of non-pollinators. This increased
pollinator production without a corresponding decrease in seed production could provide an advantage
for dioecy in conditions where pollinators are limiting.